In manufacturing a semiconductor device, there are a number of methods to perform a film forming treatment for a semiconductor wafer (hereinafter, referred as a “wafer”). Among the above methods, there is provided a treatment in which atomic or molecular layers of reaction products are stacked to perform the film forming treatment. Such treatment provides satisfactory step coverage (a characteristic of deposition) for a minute-scaled pattern and a high precision for a thin film. The film forming treatment process includes making a first gas to be absorbed to the heated wafer, then reacting the molecules of the first gas on the wafer with a second gas, and nitrifying or oxidizing the above molecules, for example. The film forming treatment is carried out by repeating the above-mentioned process for a plurality number of times.
A vertical heat treatment apparatus is used for performing this film forming treatment for a plurality of wafers collectively. For instance, silane-based gas and ammonia gas are alternately supplied into a reaction container of the vertical heat treatment apparatus from their respective gas nozzles, thereby forming a silicon nitride film on the wafer. This film forming treatment may perform a method including: installing a buffer tank at each gas supply route, storing the gas in the buffer tank, pressurizing the gas, and discharging the gas at one burst. From this method, each gas can be supplied into the reaction container as fast as possible.
During the above method, the silicon nitride film may be peeled off from the reaction container, thereby generating particles. Thus, in order to restrain the generation of the particles from the peeled off silicon nitride film, a film forming treatment for the wafer, for example, is performed. After the treatment, a thermal stress is exerted to the film by varying the temperature within the reaction container by closing the cover of the reaction container at each time, thereby forcibly peeling the film off. Such treatment may retrain the particle from being generated. However, if a gas is supplied by using the buffer tank as mentioned above, particles tend to stick to the line in the direction of the diameter on the surface of the wafer. Considering the arrangement of the particles' line and gas nozzles, the particles are spurting out from a supply route for silane-based gas.
Conventionally, there is disclosed a method of storing a dichloro-silane gas in a gas storage unit, pressurizing the gas, and then supplying it into a processing container. Then, an inert gas is supplied into the processing container through the gas storage unit, wherein the inert gas is stored in the gas storage unit exclusively for an inert gas and installed at the upstream of the gas storage unit. However, this method is different from the invention of the present disclosure.